1. Field of the Invention
The present invention relates to a use of organic dye compounds, more particularly, to an agent for inducing receptor potential, which comprises an organic dye compound(s) capable of inducing/evoking a receptor potential in response to photostimulation.
2. Description of the Prior Art
As it is well known that vision is established through sequential processes of conversion of photostimulation received from an object by the eye into electric energy; the resulting electric energy's transmission to the brain; and the brain's recognition and judgement of the color and shape of the object. Photostimulation received by the eye is converted into electric energy in the retina, and when photostimulation with a level exceeding the threshold of visual cell receptors is focused on the retina, a receptor potential is evoked in the optic nerve and then transmitted to the upper central nervous system in an impulse form. The retinal function of converting photostimulation into electric energy is quite important for establishing vision. The retinal damage induced by injuries or diseases may result in visual disorders such as narrowing of visual field, reduction of visual acuity, and nyctalopia.
At present, in Japan, it is said there are millions of patients suffering from visual disorders such as narrowing of visual field caused by retinal disorders, reduction of visual acuity, and nyctalopia. The retinal disorders are mostly evoked by diseases such as retinitis pigmentosa, age-related macular degeneration, and diabetic retinopathy. For instance, referring to retinitis pigmentosa which is an intractable disease specified as a specific disease by the Ministry of Health, Labor and Welfare of Japan, congenital disposition deteriorates retinal cells to evoke visual field scotomas, and this results in blindness after gradual progression. However, even when the retina is suffers from any disorder and, for example, in retinitis pigmentosa in which the damage only stays in visual cells so as to keep the optic nerve substantially normal conditions, artificial installation of devices for converting photostimulation into electric signals and transmitting them to the optic nerve would brighten the visual field, meaning that it would possibly improve “the quality of life”.
Now, in this field, there have been energetically progressed researches on substituent materials for the retina such as “artificial retinae” where a photosensor, mainly composed of a photoelectric-converting device such as a charge-coupled device (CCD), is formed into a chip which is then embedded in the eyeball as disclosed, for example, in Japanese Patent Kohyo Nos. 511,697/96 and 506,662/99. Since conventionally proposed artificial retinae would have difficulties in miniaturizing both photosensors and external power supplies for actuating the photosensors, it is clear that there still remain hurdles to be overcome until actual exploitation of a device that can be inserted into the eyeball for use.